Liquid stabilizer for nitrate ester compounds and method for preparing the same

Abstract

The application discloses a liquid stabilizer for nitrate compounds and a preparation method thereof, wherein phenol derivatives, glycidyl ethers and alkaline substances are added into an aqueous organic solvent under stirring at 20-30 DEG C, the mixture is stirred uniformly, then the temperature is raised to 40-80 DEG C in an oil bath to make ethanol reflux, the stirring reaction is carried out for 4-40 hours, then an extraction solvent is added after cooling, the mixture is stirred intensively and then is left to separate into layers, the extraction liquid is washed with 1M sodium hydroxide aqueous solution for three times, the organic solution layer is collected after separation and the water layer is discarded, the organic solution layer is washed with saturated sodium chloride solution for three times, and ethyl acetate is removed by rotary evaporation to obtain the product as the liquid stabilizer. The liquid stabilizer contains a large number of ether bond structures in the molecular structure, thus becoming an oxygen-containing stabilizer, and after being compounded with nitrate compounds, the liquid stabilizer less affects the fast combustion performance of the nitrate compounds.

Description

Technical Field

[0001] This invention relates to the field of organic stabilizers, specifically to a compound that stabilizes energetic materials formed by the compounding of nitrate esters and various nitrate esters, and a method for synthesizing such compounds. Background Technology

[0002] Nitrate ester compounds and complexes composed of various nitrate ester compounds are the main components of energetic materials. However, during long-term storage, nitrate ester compounds absorb trace amounts of moisture and undergo hydrolysis to generate acids, or undergo thermal decomposition to generate nitric oxide free radicals. Acids and nitric oxide free radicals can catalyze and accelerate the decomposition of nitrate esters, generating more acids and nitric oxide free radicals. Repeated cycles of autocatalytic decomposition cause a decline in the performance of energetic materials and may even lead to heating, combustion, or explosion. Therefore, it is necessary to add appropriate stabilizers (called stabilizing agents) for stabilization treatment. Currently, the stabilizers added are mainly aniline derivatives. These stabilizers can absorb the acid, nitrogen oxides and free radicals released from the decomposition of nitrate esters, thereby inhibiting the autocatalytic decomposition reaction of nitrate esters. These stabilizers include N-methyl-p-nitroaniline (MNA), diphenylamine (DPA), 2-nitrodiphenylamine (2-NDPA), N,N-diphenylurea (AK-I), N-methyl-N'-diphenylurea (AK-II), N,N'-diethyl-N,N'-diphenylurea (C1), and N,N'-dimethyl-N,N'-diphenylurea (C2).

[0003] However, aniline stabilizers exhibit slow initial nitrosation rates and have limited stabilizing effects on some nitrate ester compounds, often making them unsuitable for use alone with certain specific nitrate ester compounds. Furthermore, nitrous acid, an intermediate product of nitrate ester decomposition, can form stable nitrosamine derivatives with amine compounds. These nitrosamine derivatives are considered potent carcinogens, and the International Agency for Research on Cancer (IARC) of the World Health Organization lists several nitrosamine derivatives with different structures as carcinogens. This poses additional occupational safety risks during the processing, storage, and transportation of energetic materials using these stabilizers. Therefore, designing and synthesizing novel stabilizers that meet the stability requirements of energetic materials while being environmentally friendly and non-toxic is crucial for optimizing and improving the performance of energetic materials using nitrate ester compounds.

[0004] Based on the understanding of the decomposition and stabilization mechanisms of nitrate esters, studies have confirmed that phenolic derivatives with specific structures also exhibit good stabilizing effects on nitrate esters and may be used as stabilizers for energetic materials containing nitrate esters. For example, Krumlinde et al. reported that bis-(2,6-dimethoxyphenol)triglycine has a good stabilizing effect on nitrocellulose (Patrik Krumlinde et al., Propellants Explos. Pyrotech. 2017, 42, 78); Wang Xijie et al. published the synthesis of this compound (Wang Xijie et al., Applied Chemical Industry, 2019, 48(Supplement 2): 249); Chinese invention patents CN107032964A, CN107011128A, and CN106946664A disclose the synthesis method of this compound and its application as a stabilizer for nitrate esters. However, this phenol derivative is solid at room temperature and needs to be dissolved in a specific solvent before it can be used to prepare energetic materials. Furthermore, its stability has not been widely recognized, and it has failed to achieve large-scale production and application. Summary of the Invention

[0005] To address the problems of poor performance and easy generation of toxic substances by existing aniline derivative stabilizers, and the fact that phenol derivatives such as bis-(2,6-dimethoxyphenolyl)triglycine are solid and not conducive to large-scale application, this invention provides a phenol derivative with a novel chemical structure that is liquid at room temperature and can be used as a stabilizer for energetic materials containing nitrate ester compounds.

[0006] In a first aspect, the present invention provides a liquid stabilizer for nitrate ester compounds, having the following structure:

[0007]

[0008] Where x is a repeating unit, 1≤x≤6; n is the number of OR3, 1≤n≤5; R1 is an alkane residue, and R2 and R3 are independently selected from hydrogen atoms (H) or straight-chain alkyl groups.

[0009] Preferably, when x = 3 and n = 2, OR3 is located at positions 2 and 6, or positions 3 and 5, or positions 2 and 4; R1 is a trimethylolpropane residue, R2 = H, and R3 = CH3.

[0010] Preferably, when x=3 and n=3, OR3 is located at positions 2, 4 and 6; R1 is a trimethylolpropane residue, R2=H, and R3=CH3.

[0011] Preferably, when x = 4 and n = 2, OR3 is located at positions 2 and 6, or at positions 3 and 5, or at positions 2 and 4; R1 is a pentaerythritol residue, R2 = H, and R3 = CH3.

[0012] Preferably, when x = 4 and n = 3, OR3 is located at positions 2, 4, and 6; R1 is a pentaerythritol residue, R2 = H, and R3 = CH3.

[0013] Preferably, when x = 3 and n = 2, OR3 is located at positions 2 and 6; R1 is a trimethylolpropane residue, R2 = CH3, and R3 = CH3.

[0014] Preferably, when x = 4 and n = 2, OR3 is located at positions 2 and 6; R1 is a pentaerythritol residue, R2 = CH3, and R3 = CH3.

[0015] Preferably, when x = 6 and n = 2, OR3 is located at positions 2 and 6; R1 is a dipentaerythritol residue, R2 = CH3 or H, and R3 = CH3.

[0016] In a second aspect, the present invention provides a method for synthesizing the liquid stabilizer described in the first aspect, comprising:

[0017] The steps for preparing the target product liquid stabilizer involve reacting a phenol derivative and glycidyl ether in an aqueous organic solvent under alkaline conditions.

[0018]

[0019] Preferably, the phenol derivatives include, but are not limited to, phenol (n=0), alkoxyphenols (1≤n≤5), and alkylphenols, with alkoxyphenols and alkylphenols being more preferred. Alkoxyphenols include, but are not limited to, 2,4-dimethoxyphenol, 2,6-dimethoxyphenol, 3,5-dimethoxyphenol, 2,4,6-trimethoxyphenol, 2,4-diethoxyphenol, 2,6-diethoxyphenol, 3,5-diethoxyphenol, 2,4,6-triethoxyphenol, 2,4-dipropoxyphenol, 2,6-dipropoxyphenol, 3,5-dipropoxyphenol, 2,4,6-triethoxyphenol, 2,4-dipropoxyphenol, 2,6-dipropoxyphenol, 3,5-dipropoxyphenol, 2,4,6-tripropoxyphenol, 2,4-dipropoxyphenol, 2,6-dipropoxyphenol, 3,5-dipropoxyphenol, 2,4,6 ...6-dipropoxyphenol, 2,4,6-dipropoxyphenol, 2,6-dipropoxyphenol, 2,4,6-dipropoxyphenol, 2,6-dipropoxyphenol, 2,6-dipropoxyphenol, 2,4,6-dipropoxyphenol, 2,6-dipropoxyphenol, 2,6-dipropoxyphenol, 2,4 One or more of the following: oxyphenol, 2,4-diisopropoxyphenol, 2,6-diisopropoxyphenol, 3,5-diisopropoxyphenol, 2,4,6-triisopropoxyphenol, 2,4-di-tert-butoxyphenol, 2,6-di-tert-butoxyphenol, 3,5-di-tert-butoxyphenol, and 2,4,6-tri-tert-butoxyphenol; alkylphenols, including but not limited to o-methylphenol, m-methylphenol, p-methylphenol, and o-ethylphenol. m-Ethylphenol, p-Ethylphenol, o-Propylphenol, m-Propylphenol, p-Propylphenol, o-Isopropylphenol, m-Isopropylphenol, p-Isopropylphenol, m-T-Butylphenol, p-T-Butylphenol, 2,4-Dimethylphenol, 2,6-Dimethylphenol, 3,5-Dimethylphenol, 2,4,6-Trimethylphenol, 2,4-Diethylphenol, 2,6-Diethylphenol, 3,5-Diethylphenol, 2,4,6-Trimethylphenol One or more of ethylphenol, 2,4-dipropylphenol, 2,6-dipropylphenol, 3,5-dipropylphenol, 2,4,6-tripropylphenol, 2,4-diisopropylphenol, 2,6-diisopropylphenol, 3,5-diisopropylphenol, 2,4,6-triisopropylphenol, 2,4-di-tert-butylphenol, 2,6-di-tert-butylphenol, 3,5-di-tert-butylphenol, and 2,4,6-tri-tert-butylphenol.

[0020] Preferably, the glycidyl ethers include, but are not limited to, one or more of the following: ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,4-cyclohexanediol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol A propoxylated diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, castor oil triglycidyl ether, pentaerythritol tetraglycidyl ether, dipentaerythritol hexaglycidyl ether, and sorbitol hexaglycidyl ether.

[0021] Preferably, the reaction between glycidyl ether and phenol derivative is carried out under alkaline conditions, and the alkaline substances used include, but are not limited to, one or more combinations of lithium hydroxide, potassium hydroxide, potassium hydride, sodium hydroxide, sodium hydride, potassium carbonate, sodium carbonate, potassium methoxide, sodium methoxide, butyllithium, diisopropylamine lithium, benzyllithium, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium amino, and sodium amino.

[0022] Preferably, the organic solvent in the aqueous organic solvent includes, but is not limited to, one or more of methanol, ethanol, propanol, n-butanol, tert-butanol, ethylene glycol, glycerol, diethyl ether, methyl ethyl ether, acetone, butanone, dimethyl formamide, dimethyl sulfoxide, acetonitrile, and dioxane, and the volume ratio of the organic solvent to water in the aqueous organic solvent is 1:1.

[0023] Preferably, the reaction temperature is between room temperature and the boiling point of the solvent, with a preferred reaction temperature of 40-80°C, and the reaction time ranges from a few minutes to tens of hours, with a preferred reaction time of 4-40 hours.

[0024] Preferably, the product is separated and purified by extraction after the reaction. Depending on the solvent system, the extraction solvents that can be used include, but are not limited to, one or more combinations of methyl formate, ethyl formate, propyl formate, isopropyl formate, butyl formate, isobutyl formate, isoamyl formate, benzyl formate, methyl acetate, ethyl acetate, ethyl acetoacetate, n-propyl acetate, n-butyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, methyl amyl acetate, methyl propionate, n-butyl propionate, amyl propionate, methyl butyrate, ethyl butyrate, n-butyl butyrate, diethyl oxalate, and dibutyl oxalate.

[0025] Thirdly, the present invention provides the use of the liquid stabilizer described in the first aspect in a propellant.

[0026] Compared with existing technologies, the beneficial effects of this invention are as follows: the liquid stabilizer for nitrate ester compounds is liquid at room temperature and easily mixes and dissolves with nitrate ester compounds to form a homogeneous system. Oxygen-containing, liquid phenol derivatives, after being compounded with nitrate ester compounds, do not produce carcinogenic nitrosamines, thus exhibiting characteristics such as low toxicity, soluble (soluble in conventional solvents) or liquid state, and no interference with the curing of nitrate ester compounds. The liquid stabilizer for nitrate ester compounds contains a large number of ether bonds in its molecular structure, thus becoming an oxygen-containing stabilizer, and after being compounded with nitrate ester compounds, it has minimal impact on the rapid combustion performance of nitrate ester compounds; this opens a new path for the development of energetic materials such as propellants based on nitrate ester compounds. Attached Figure Description

[0027] Figure 1 The infrared spectrum of product 01 obtained in Example 1 is shown.

[0028] Figure 2 The image shows the hydrogen nuclear magnetic resonance spectrum of product 01 obtained in Example 1.

[0029] Figure 3 The image shows the ultraviolet spectrum of product 01 obtained in Example 1.

[0030] Figure 4 This is the liquid chromatogram of product 01 obtained in Example 1.

[0031] Figure 5 This illustrates the effect of different reaction media on product yield in Example 7.

[0032] Figure 6 The color changes of different samples before heating (a) and after heating (b) in Application Example 2 are shown. Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.

[0034] Example 1

[0035] In a 250 mL flask equipped with a reflux condenser, stirrer, thermometer, and other auxiliary equipment, 30 g of trimethylolpropane triglycidyl ether, 46 g of 2,6-dimethoxyphenol, 5 g of potassium carbonate, and an aqueous organic solvent (100 mL of ethanol and 100 mL of water) were added at room temperature. The mixture was stirred until homogeneous, and the mixture was gradually heated in an oil bath to allow the ethanol to reflux. The reaction was maintained with stirring for 20 hours. After cooling, 100 mL of ethyl acetate was added, and the mixture was stirred vigorously and allowed to stand to separate into layers. The upper extract was collected, and the lower layer was extracted twice with 100 mL of ethyl acetate each time. The extracts were combined, and the mixture was washed three times with 50 mL of 1M sodium hydroxide aqueous solution each time. The aqueous layer was discarded, and the organic solvent layer was collected. The organic solvent layer was then washed three times with 150 mL of saturated sodium chloride solution. The ethyl acetate was removed by rotary evaporation, yielding approximately 60 g of product O1.

[0036] Product 01 was analyzed by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, and liquid chromatography, and the results are as follows: Figures 1 to 4 As shown. Figure 1 and Figure 2 The chemical structure of product 01 was revealed. Figure 3 and Figure 4 This proves that product 01 has a purity of 98%.

[0037] Example 2

[0038] Similar to Example 1, but 2,6-dimethoxyphenol was replaced with 3,5-trimethoxyphenol, yielding approximately 58g of product O2.

[0039] Example 3

[0040] Similar to Example 1, but 2,6-dimethoxyphenol was replaced with 2,4-trimethoxyphenol, yielding approximately 50g of product 03.

[0041] Example 4

[0042] Similar to Example 1, but 30g of trimethylolpropane triglycidyl ether was replaced with 36g of pentaerythritol tetraglycidyl ether, and 62g of 2,6-dimethoxyphenol was added. Methanol was used as the solvent, and the mixture was stirred and refluxed at 60°C for 40 hours. The mixture was then extracted with butyl acetate to finally obtain approximately 80g of product 05.

[0043] Example 5

[0044] Similar to Example 1, but 30g of trimethylolpropane triglycidyl ether was replaced with 60g of dipentaerythritol hexaglycidyl ether, and 92g of 2,6-dimethoxyphenol was added. Dimethylformamide was used as a solvent, and the mixture was stirred at 80°C for 8 hours. The mixture was then extracted with butyl acetate to finally obtain approximately 100g of product 11.

[0045] Example 6

[0046] Based on Example 5, product 11 was reacted with iodomethane under reflux in a methanol / sodium methoxide solution, then thoroughly washed with water and dried to obtain product 12.

[0047] Example 7: Effect of Reaction Medium on Product Yield

[0048] The other processes are the same as in Example 1, except that the aqueous organic solvent is replaced with acetonitrile, methanol, water, ethanol, and their mixtures. This experiment used different reaction media to prepare stabilizers and tested the synthesis yield of stabilizers in solvents. The results are as follows: Figure 5 As shown.

[0049] Depend on Figure 5 It can be seen that due to the low solubility of acetonitrile in KOH, it is difficult to provide a sufficiently alkaline environment, which is detrimental to the removal of small molecule HCl, resulting in a low synthesis yield. Methanol and ethanol also show similar issues, and small molecule alcohols also partially participate in side reactions, making product purification difficult and leading to a low overall yield.

[0050] Analysis showed that using a mixed solvent of ethanol and water as the reaction medium improves the solubility of KOH, reduces reaction costs, and also enhances the safety of the medium. Figure 5 As shown, when using an ethanol-water mixed solvent as the reaction medium, the synthesis yield is significantly higher than that of a single reaction medium, and the yield reaches its highest when the ratio of ethanol to water is 1:1.

[0051] Application Example 1: Compatibility of Stabilizer and Propellant Components

[0052] The compatibility test between product 01 in Example 1 and the double-base propellant was performed according to method 502.1 of GJB772A-97, and the results are shown in Table 1.

[0053] Table 1 Compatibility of stabilizer (product 01) with double-base propellant

[0054]

[0055] a.ΔT p ≤2.0℃, ΔE / E≤20%, good compatibility, Class I;

[0056] b.ΔT p ≤2.0℃, ΔE / E>20%, good compatibility, grade 11;

[0057] c.ΔT p >2.0℃, ΔE / E≤20%, poor compatibility, Class 111:

[0058] d.ΔT p >2.0℃, ΔE / E>20%, poor compatibility, Class IV.

[0059] Application Example 2: Stability Testing

[0060] (1) Color judgment

[0061] Product 01 from Example 1 and diphenylamine were mixed with nitrocellulose at a mass ratio of 1% each, and then dried to obtain Sample 1 and Sample 2. Images of Sample 1 and Sample 2 before heating are shown below. Figure 6 As shown in Figure a, Sample 1 and Sample 2 were placed in an 80℃ oven and heated for 14 days. After 14 days, the two samples were compared. Figure 6 As shown in b, the results show that product 01 has a similar stability to diphenylamine.

[0062] (2) Vierry and Methyl Violet Test

[0063] The stability of product 01 from Example 1 and the double-base propellant was determined by vitriol and methyl violet tests according to GJB770B method 503.1 and GJB770B method 503.3, respectively. The results are shown in Table 2.

[0064] Table 2. Test results of Vieryl and Methyl Violet in samples.

[0065]

[0066] Note: The passing criteria for the 106.5℃ Vieri test are 7-7 hours for the ordinary method and 70-70 hours for the repeated method; the passing criteria for the 120℃ methyl violet test are color change time > 60 minutes and non-explosive time > 5 hours.

[0067] As can be seen from Table 2, all products 01 passed the Vierry and Methyl Violet tests, demonstrating stability comparable to existing stabilizers.

[0068] Application Example 3: Effect of Stabilizers on Propellant Combustion Performance

[0069] The propellant was prepared according to the formula in Table 3, and the combustion performance of the prepared propellant was tested. The results are shown in Table 4.

[0070] Table 3 Double-base propellant formulations

[0071]

[0072] Table 4. Combustion performance and heat of explosion test results

[0073]

[0074] As shown in Table 4, replacing C2 with 0.7% product 01 increased the propellant heat of explosion by 14 KJ / Kg; replacing C2 with 1.2% product 01 increased the propellant heat of explosion by 34 KJ / Kg; the preliminary judgment is that the heat of explosion coefficient of product 01 is about -16.6 KJ / Kg, and the heat of explosion coefficient of C2 is about -22.5 KJ / Kg.

[0075] After replacing part of C2 with product 01, the propellant heat generation increased, mainly because the stabilizer structure prepared in this invention contains oxygen.

[0076] Molecular simulation calculations show that the oxygen content in the product 01 molecule reaches 30.3%, while the C2 stabilizer molecule contains no oxygen. Therefore, the stabilizer of the present invention is beneficial to improving the energy characteristics of the propellant, which is consistent with the experimental results.

[0077] Application Example 4: 7-day accelerated aging test with stabilizer

[0078] Accelerated aging tests were conducted according to GJB770B-2005 "Test Methods for Gunpowder - Method 506.1 Predicted Safe Storage Life - Accelerated Aging Method". The reference sample was prepared by dissolving 70% nitrocellulose (1% C2, 12.6% nitrogen content) and 29% nitroglycerin in a mixed solvent of ethanol and acetone, mixing thoroughly, casting into thin sheets, and then drying. The test samples were prepared by dissolving 1% of a synthesized stabilizer (product 01), 70% nitrocellulose (12.6% nitrogen content), and 29% nitroglycerin in a mixed solvent of ethanol and acetone, mixing thoroughly, casting into thin sheets, drying, and then testing. The test results are shown in Table 5.

[0079] Table 570℃ Accelerated Aging Effective Stabilizer Content

[0080]

[0081] Based on the effective stabilizer content, the estimated safe storage life of product 01 in double-base propellant is greater than that of stabilizer C2.

[0082] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 3, n = 2, OR3 is located at positions 2 and 6, or at positions 3 and 5, or at positions 2 and 4; R1 is a trimethylolpropane residue, R2 = H, R3 = CH3.

2. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 3, n = 3, OR3 is located at positions 2, 4 and 6; R1 is a trimethylolpropane residue, R2 = H, R3 = CH3.

3. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 4, n = 2, OR3 is located at positions 2 and 6, or at positions 3 and 5, or at positions 2 and 4; R1 is a pentaerythritol residue, R2 = H, R3 = CH3.

4. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 4, n = 3, OR3 is located at positions 2, 4 and 6; R1 is a pentaerythritol residue, R2 = H, R3 = CH3.

5. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 3, n = 2, OR3 is located at positions 2 and 6; R1 is a trimethylolpropane residue, R2=CH3, R3=CH3.

6. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 4, n = 2, OR3 is located at positions 2 and 6; R1 is a pentaerythritol residue, R2=CH3, R3=CH3.

7. A liquid stabilizer for nitrate ester compounds, characterized in that, It has the following structure: ； x = 6, n = 2, OR3 is located at positions 2 and 6; R1 is a dipentaerythritol residue, R2 = CH3 or H, R3 = CH3.

8. Use of a liquid stabilizer as described in any one of claims 1-7 in stabilizing nitrate ester compounds.

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